Andy Rubin is a man of few words, at least on Twitter. Followed by 15,000, he only ever tweeted once before today, defending Android's openness. His second tweet - an update on the daily rate of Android activations, which was 100,000 per day in May during Google I/O, 160,000 in June, 200,000 in August, and now topped 300,000.

300,000 Android phones a day! That's 2.1 million phones per week, about 9 million phones per month, or 108 million phones per year. That's a whole lot of phones.

Just for fun, I entered the data points into a spreadsheet and extrapolated them using a trendline. Of course, the growth can't continue forever, but using the current data points, we'd reach 500,000 daily activations sometimes in mid-2011, and by the end of next year, Android would be around 650,000. Go Android!